import java.util.LinkedList;
import java.util.Queue;

class MyStack {

    Queue<Integer> qu1;
    Queue<Integer> qu2;
    public MyStack() {
        qu1 = new LinkedList<>();
        qu2 = new LinkedList<>();
    }
    
    public void push(int x) {
        if (!qu1.isEmpty()) {
            qu1.offer(x);
        } else if (!qu2.isEmpty()) {
            qu2.offer(x);
        } else {
            qu1.offer(x);
        }
    }
    
    public int pop() {
        if (empty()) {
            return -1;
        }

        if (!qu1.isEmpty()) {
            int size = qu1.size();
            for (int i = 0; i < size - 1; i++) {
                qu2.offer(qu1.poll());
            }
            return qu1.poll();

        } else {
            int size = qu2.size();
            for (int i = 0; i < size - 1; i++) {
                qu1.offer(qu2.poll());
            }
            return qu2.poll();
        }
    }
    
    public int top() {
        if (empty()) {
            return -1;
        }

        if (!qu1.isEmpty()) {
            int size = qu1.size();
            for (int i = 0; i < size - 1; i++) {
                qu2.offer(qu1.poll());
            }
            int top = qu1.poll();
            qu2.offer(top);
            return top;
        } else {
            int size = qu2.size();
            for (int i = 0; i < size - 1; i++) {
                qu1.offer(qu2.poll());
            }
            int top = qu2.poll();
            qu1.offer(top);
            return top;
        }
    }
    
    public boolean empty() {
        return qu1.isEmpty() && qu2.isEmpty();
    }

    public static void main(String[] args) {
        MyStack stack = new MyStack();
        stack.push(1);
        stack.push(2);
        stack.push(3);
        System.out.println(stack.top());
    }
}